Process and composition for use in color photography



Patented Apr. 20, 1954 PROCESS AND COMPOSITION FOR USE IN COLOR PHOTOGRAPHY George Steans, New York, N. Y., assignor to The FR Corporation, New York, N. Y., a corporation of New York No Drawing. Application March 18, 1950, Serial No. 150,559

11 Claims.

The present invention relates to an improved photographic composition and method, and it relates more particularly to an improved composition and method employed in the field of color development in photography.

The methods now almost universally employed in the production of colored images in photography consist in producing by suitable exposure to light a latent image in the silver halide containing emulsion. The silver halide which has been exposed to form the latent image is then reduced or developed in the presence of a coupler by a developer having certain desired char acteristics. A coupler is a compound. which is converted or precipitated as a dye in the vicinity of a latent image during the development or the image as a result of its reaction or coupling with the product resulting from the action of the light exposed silver halide on a suitable developer.

There are numerous chemical compounds which may be used as couplers. These are characterized by their ability to produce reaction products with an oxidized suitable developer which contain an azomethine group which is a chromophore and/or other chromophoric or auxochromic groups. These reaction products are, therefore, dyes and these dyes are precipita ed as aforesaid adjacent to the reduced silver of the photographic image. If the image produced is bleached, only the dye image remains. Examples of couplers mentioned in the literature are for instance naphthol, acetoacet-2.5 dichloranilide, and p-nitrophenylacetonitrile.

The p-phenylenediamine type developers have been widely employed as coupling developers. These are derived from the mother substance by substitutions in the amino group or in the ben zene ring or by substitutions in the amino group as well as in the benzene ring. However, a primary amino group has to be retained so that coupling can proceed. P-aminophenol derivatives containing a primary amino group and also certain heterooyclic organic compounds have been used as coupling developers.

Two procedures employing couplers have generally been followed in the production of colored photographic images. In the first of these, typifled by the Kodachrome process, the coupler is dispersed in and made part of the sensitized It is with the second process that the present invention is primarily concerned. In this second process, a coupler, which is practically insoluble in water, can be dissolved in organic solvents or aqueous solutions of high alkalinity. The solution containing the coupler is added to the alkaline solution of the developer and the photographic material is processed therewith and colored images produced as above described.

However, in practicing the process, the addition of solutions of couplers dissolved in acetone as the usually employed solvent, or in alkalies. increases the alkalinity of the original aqueous solution of the developer. This increase in pH is further uncontrollable due to the fact that varying quantities of coupler solution have to be added so that the developed image can be obtained with desired shades. The increase of alkalinity may produce overall densities which can be described as colored fog. Furthermore, the increase of alkalinity is also detrimental to the keeping properties of such solutions which will be oxidized very rapidly and the dye formed thereby will stain the highlights of the image.

Another drawback of using solutions of 0011- plers in acetone and other organic solvents is the property of the solvent to evaporate leaving solutions of couplers more concentrated expected and, therefore, producing unexpected. shades. Moreover, such solutions evaporate frequently to dryness and are then, of course, unusable. The inflammability of the solvents and the consequent fire hazard is another serious disadvantage.

It is, therefore, a principal object of the pres ent invention to provide an improved method and composition for the development of colored photographic images.

Another object of the present invention is to provide an improved method and composition for the development of colored photographic images characterized by their simplicity of application and the uniformity of results.

Still another object of the present invention is to provide an improved method and composi tion for the development of colored photographic images which is characterized by the keeping properties and the 'non-inflammability of the ingredients.

A further object of the present invention is to provide a composition for the development of colored photographic images which composition is characterized by the absence of deterioration.

Still a further object of the present invention is to provide an improved method and composition for the development of colored photographic images characterized by the uniformity of results obtainable with a minimum of process control.

The above and other objects of the present invention will become apparent from a reading of the following description in which several illustrations will be given.

The present invention broadly contemplates processing a latent image in an aqueous alkaline solution of a coupler and a suitable developer, bufiered to maintain a. pH which will produce true color condition, Another feature forming a part of the present invention is the method and composition for achieving the above solution. This is accomplished by finely comminuting the coupler and admixing it with a larger amount of a solid water soluble carrier. This carrier may be a soluble inorganic salt, neutral, alkaline or acid in accordance with the desired shade or color to be achieved.

More particularly, an emulsion containing a silver halide latent image is processed in a buffered alkaline solution of a coupler, a suitable developer and one or more inorganic salts which produce the desired pH and hence the desired shade or color. All the ingredients entering into the aqueous solution can be solids, not subject to deterioration. Moreover, by admixing the coupler in a finely divided form with a soluble salt all the ingredients can be easily dissolved in water to produce the developing solution. Thus, the ingredients forming the color developing solution can be easily stored in dry form and dissolved in water in predetermined proportions when the developing solution is desired. Since no volatile solvents are employed and the ingredients do not deteriorate, the process control is a very simple matter. It has been found that the coupler is readily soluble in the alkaline aqueous solution of the developer if it has an average particle size of the range of about 100 microns and is dispersed in one or more dry water soluble salts. It is apparent that finer particle sizes are at least equally effective and in many cases coarser particle sizes may be employed.

The following are specific examples of color developing solutions according to the present invention which may be employed in the same manner as solutions heretofore employed have been used, such procedure being well known in the art:

For obtaining a blue image, the following ingredients in the proportions shown are stored, until used in a dry form as three separate powders as indicated .by the letters A, B and C:

Grams (A) Sodium sesquicarbonate 5.0

(B) 2 amino-5 diethyl amino toluene hydrochloride .2 Sodium sulfite .8 Sodium sulfate 4.0

(C) 2, 4 dichloro naphthol .162

Sodium chloride 2.0 Sodium bisulfite 3.0

The above powders are dissolved in water to make a twelve ounce solution and may be dissolved in any order. The pH of the resulting solution should be approximately 8.5 and is ernployed in a manner well known in the art.

In order to obtain a sepia image, the following ingredients are employed in the manner above set forth and are dissolved in water to make a twelve ounce solution having a pH of approximately 10.5:

Grams (A) Sodium sesquicarbonate 5.0

(B) 2 amino-5 diethyl amino toluene hydrochloride .2

Sodium sulfite .8

Sodium sulfate 4.0

(C) P-nitrophenyl aceto nitrile .03

Aceto acet 2-5 dichloranilide .09

Sodium chloride 1.0

Sodium carbonate 4.0

A red image may be secured by employing the following ingredients as above set forth, the twelve ounce solution thereof having a pl-I of approximately 9.5:

Grams (A) Sodium sesquicarbonate 5.0

(B) 2 amino-5 diethyl amino toluene hydrochloride .2

Sodium sulfite .8

Sodium sulfate 4.0

(C) P-nitro phenyl aceto nitrile l .1

Sodium chloride 2.0

Sodium sulfate 3.0

As has been noted, the shades achieved can be varied by adjusting the pH of the solution. This is preferably accomplished by employing salts of the desired acidity or alkalinity admixed with the coupler. Any salts which are compatible with the other ingredients with no ill eiiect may be employed.

In producing the salt coupler mixture, the coupler and one or more salts are ground together in the required proportions until the particle size of the coupler has reached the fineness desired as above set forth. Furthermore, while the proportion by weight of coupler to salt carrier in the examples given is approximately 1:50, this may be varied to suit the prevailing conditions. However, the proportion of carrier to coupler should be large enough to facilitate the dissolving of the coupler into aqueous solution. This proportion may be as large as several hundred or thousand to one.

While there has been described several examples embodying the present invention, it is obvious that numerous alterations and omissions can be made without departing from the spirit thereof.

Having now described my invention, what I claim and desire to secure by Letters Patent is:

l. The method of producing a colored image from a silver halide latent image comprising reducing the silver halide with an alkaline aqueous solution containing sodium sesquioarbonate, at least one more inorganic salt, a coupler and a p-phenylenediamine developer whose oxidation product reacts with said coupler to form a dye in the vicinity of said latent image thereby producing a colored image.

2. The method as claimed in claim 1 wherein the pH of said solution is in excess of 8.5.

3. The method of claim 1 wherein said coupler is selected from the classes of organic compounds which form azomethine dyes with the oxidized developer.

4. The method asclaimed in claim 1' wherein said coupler is selected from the class consisting of naphthol, acetoacet2.5 dichloranilide and p-nitrophenylacetonitrile. V

5. A color forming photographic developer Parts Sodium sesquicarbonate 5.0 2 amino-5 diethyl amino toluene hydrochloride .2 Sodium sulfite .8 Sodium sulfate 4.0 2,4 dichloro naphthol .162 Sodium chloride 2.0

Sodium loisulfite 3.0

8. A color forming photographic developer comprising the following ingredients in substantially the proportions shown:

Parts Sodium sesquicarbonate 5.0 2 amino-5 diethyl amino toluene hydrochloride .2 Sodium sulfite .8 Sodium sulfate 4.0- P-nitrophenyl aceto nitrile .03 Acetoacet 2-5 dichloranilide .09 Sodium chloride 1.0 Sodium carbonate 4.0

9. A color forming photographic developer comprising the following ingredients in substantially the proportions shown:

Parts Sodium sesquicarbonate 5.0 2 amino-5 diethyl amino toluene hydrochloride .2 Sodium sulfite .8 Sodium sulfate 4.0 P-nitro phenyl aceto nitrile .1 Sodium chloride 2.

Sodium sulfate 3.0

10. A color forming photographic developer comprising sodium sesqui-carbonate, a p-phenylenediamine developer and a compound which will couple with the oxidation product of the developer to form a colored dye, said developer being characterized by the substantial absence of alkali and organic solvents.

11. The method of producing a colored image from a silver halide latent image comprising reducing the silver halide with an alkaline aqueous solution containing sodium sesqui-carbonate, at least one more inorganic salt, a coupler and a pphenylenediamine developer whose oxidation product reacts with said coupler to form a dye in the vicinity of said latent image thereby producing a colored image, said aqueous solution being characterized by the substantial absence of alkali and organic solvents.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 935,115 Kelly Sept. 28, 1909 1,102,028 Fischer June 30, 1914 2,271,229 Peterson Jan. 27, 1942 2,301,387 Evans et al. Nov. 10, 1942 2,324,123 Weissberger July 13, 1943 2,417,514 Neumann Mar. 18, 1947 2,592,243 Carroll et al Apr. 8, 1952 

5. A COLOR FORMING PHOTOGRAPHIC DEVELOPER COMPRISING SODIUM SESQUICARBONATE, A P-PHENYLENEDIAMINE DEVELOPER AND A COMPOUND WHICH WILL COUPLE WITH THE OXIDATION PRODUCT OF THE DEVELOPER TO FORM A COLORED DYE. 